精密旋转岩石试验机电液伺服系统的设计与研究

发布时间：2018-10-20 13:04

【摘要】：岩石力学试验机的发展水平决定着多项研究的深度与广度。现有的岩石力学试验机大多只能通过加载,获得岩石的应力-应变曲线等宏观力学特性,但无法获知岩石内部的细观结构破裂演进机制及内部物质运移规律。本课题致力于研制一种新型的岩石力学试验机,在对岩石进行加载的同时,借助高能加速器CT技术,实现压裂过程的实时成像,这就需要试验机在加载的同时精密旋转。根据新型试验机的工况,论文提出了一种全新的机械结构,并针对新结构,完成了试验机电液伺服系统的各项设计。通过对系统的建模和仿真,证明了方案的可行性。最后,完成了试验机的加工、组装、调试,并进行了加载实验。新型试验机没有采用传统的支柱式反力架结构,而是用压力室室壁充当反力架。这种结构可以使轴向加载时的剧烈变载荷成为试验机的内力,从而保证了旋转精度,为CT成像创造了条件。论文完成了试验机的机械结构设计、液压回路设计、泵站设计、供液系统设计、电控系统设计、密封设计等。加工并组装了伺服缸、增压缸、压力室、通液板、通液法兰、液压集成板、电液旋转接头等重要零件。完成了电液伺服阀、位移传感器、压力传感器、控制器等的选型和调试。针对试验机的特点,提出了一种岩石应力应变峰后曲线的探测方法。由于轴向加载伺服缸和围压加载增压缸为非对称缸,论文使用了一种利用等效承压面积加权平均的方法和液压弹簧刚度理论建立的零开口阀控非对称缸系统的线性模型,用参数加权平均的方法统一了两个方向上不同的系统模型。论文进行了理论建模+Simulink仿真、AMESim-Simulink联合仿真以及AMESim综合建模仿真。三种方式互为补充,互相比较,得到了轴向力加载响应速度可达0.4s,动态响应频率可达5.4Hz。试验机进行了静态加载实验和动态加载实验。静态实验得到了无围压与有围压时的整机刚度,结果显示20MPa围压液对整机刚度无显著影响,均为0.32GN/m。动态实验中,对轴向力控系统输入0.5Hz至5Hz的正弦信号,根据输入输出曲线,低频时跟踪良好,5Hz时输出的相位滞后仅有54度,幅值无明显衰减;位置控制模式下,阶跃响应的稳态误差小于0.001mm,对1Hz的正弦输入跟踪良好。这与仿真结果基本吻合,可以胜任十吨级岩石力学试验机的工作要求。
[Abstract]:The development level of rock mechanics testing machine determines the depth and breadth of many studies. Most of the existing rock mechanics testing machines can only obtain the macroscopic mechanical properties of rock such as stress-strain curves by loading, but it is impossible to know the evolution mechanism of the mesoscopic structure and the internal material migration law of the rock. This paper is devoted to the development of a new rock mechanics testing machine, which can realize the real-time imaging of fracturing process with the help of high energy accelerator CT technology while loading the rock, which requires the testing machine to rotate precisely while loading. According to the working condition of the new type of testing machine, a new mechanical structure is put forward, and the design of the electro-hydraulic servo system of the testing machine is completed in the light of the new structure. The feasibility of the scheme is proved by modeling and simulation of the system. Finally, the machining, assembling, debugging and loading experiment of the testing machine are completed. The new testing machine does not adopt the traditional support structure, but uses the pressure chamber wall as the counterforce frame. This structure can make the violent variable load under axial loading become the internal force of the testing machine, thus ensure the rotation accuracy and create the condition for CT imaging. The mechanical structure design, hydraulic circuit design, pump station design, liquid supply system design, electronic control system design, seal design and so on have been completed in this paper. Some important parts such as servo cylinder, pressurized cylinder, pressure chamber, hydraulic plate, hydraulic flange, hydraulic integrated plate, electro-hydraulic rotary joint and so on have been fabricated and assembled. Complete the selection and debugging of electro-hydraulic servo valve, displacement sensor, pressure sensor, controller and so on. According to the characteristics of the testing machine, a method for detecting the post-peak curves of rock stress and strain is proposed. Because the axial loading servo cylinder and the confining pressure pressurized cylinder are asymmetric cylinders, a linear model of zero opening valve controlled asymmetric cylinder system is established by using the method of weighted average area under equivalent pressure and the theory of hydraulic spring stiffness. Two different system models in different directions are unified by the method of parameter weighted average. In this paper, theoretical modeling and Simulink simulation, AMESim-Simulink joint simulation and AMESim integrated modeling and simulation are carried out. Compared with each other, the response speed of axial force loading can reach 0.4 s, and the dynamic response frequency can reach 5.4 Hz. Static and dynamic loading experiments were carried out on the tester. The stiffness of the whole machine without and with confining pressure is obtained by static experiment. The results show that the 20MPa confining pressure fluid has no significant effect on the stiffness of the whole machine, which is 0.32 GNR / m. In dynamic experiment, the sinusoidal signal from 0.5Hz to 5Hz is input to the axial force control system. According to the input and output curves, the low frequency tracking is good, the phase lag of 5Hz is only 54 degrees, and the amplitude has no obvious attenuation. The steady-state error of step response is less than 0.001mm, and the sinusoidal input of 1Hz is tracked well. The results are in good agreement with the simulation results and can meet the requirements of the ten-ton rock mechanics testing machine.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH87;TH137

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